1. Field of the Invention
This invention relates to automobile ignition systems. More specifically, this invention relates to early automobile electronic ignition systems.
2. Prior Art
FIG. 1 depicts an example of an early automobile ignition system. An example of an automobile that used such a system was the Ford Model T. For the purposes of discussion that follows, the term early refers to automobiles produced between the years of 1900 and 1930. The main components of the system comprise commutator 5, coil primary wires 1, coil box 6 containing ignition coils, spark plug wires 7 used to carry high voltage spark to their corresponding spark plugs 14. Note that commutator 5 is sometimes referred to as a Timer.
The basis of operation of this system is 100 year old technology and is well known to those skilled in the art. A brief summary of the essential elements as they pertain to the subject of the present invention will be covered. A simplified schematic diagram for the early ignition system is illustrated in FIG. 2. Ignition switch 18 is closed to provide power from battery 11 to each of the coils 13 contained within coil box 6. Actuation of each coil 13 is controlled by commutator 5 which is physically connected to and operated by the automobile engine CAM shaft that rotates when the engine is cranked. Ignition coils 13 are actuated sequentially by commutator 5 grounding their respective primary windings via wires 1 to engine ground which is typically connected to the negative terminal of battery 11. Coil actuation results in a self oscillation of primary current resulting in the generation of high voltage pulses on their corresponding secondary winding output. The high voltage pulses from the ignition coil secondary are carried to the respective engine spark plugs 14 via wires 7. The spark timing must be manually altered by the user as engine speed changes for optimum engine operation. This is accomplished by mechanically rotating commutator 5 with respect to its mounting position on the engine which effectively changes its relationship to the engine CAM shaft position and hence advances or retards the ignition timing.
FIG. 3 illustrates details of commutator 5. The coil primary wires of ignition coils are connected to commutator terminals 2. Each terminal is connected to a corresponding independent electrical contact 3 within the commutator housing. Roller 4 comprises a metal wheel physically and electrically connected to engine CAM shaft 8 that rotates when the engine CAM shaft rotates. Roller 4 functions to provide electrical connection between terminals 3 and the CAM shaft which is also connected to engine ground, most often the negative terminal of the battery 11 of FIG. 2. Ignition coil wires 1 connected to commutator terminals 2 are thus electrically connected to engine ground sequentially as roller 4 rotates, connecting their respective electrical contact 3 to the CAM shaft ground which is also engine ground. Ignition coil actuation occurs when its respective terminal on commutator 5 is grounded by roller 4 as described previously.
FIG. 4 illustrates an example of prior art that attempts to improve upon the original ignition system of FIG. 2 by eliminating reliance on physical mechanical contact between roller 4 and electrical contacts 3 of FIG. 3 in order to actuate associated ignition coils 13. This is accomplished by replacing the mechanical electrical contacts 3 of FIG. 3 with circuit board 21 containing modern electronic sensors 10 and replacing roller 4 of FIG. 3 with rotor 20 that is still physically attached to engine CAM shaft 8. Rotor 20 contains one or more sensor actuators 9 employed to actuate sensors 10 as they are rotated by the CAM shaft. CAM shaft position sensing is not new or novel. The sensors and sensor actuators may take the form of optical or magnetic or vein. CAM shaft position sensing and operation are well known to those skilled in the art. Electrical contact terminals 2 are no longer used to actuate ignition coils 13. Select commutator terminals 2 are now used to signal CAM shaft position when sensors 10 are responsive to CAM shaft sensor activators 9. Another commutator terminal 2 function is changed to supply an independent source of external DC power to sensors 10 and the remaining commutator terminal 2 is changed to provide connection to engine ground as a DC power return. Hence, the purpose, wiring and operation of commutator 5 is completely different from the original vintage ignition system. A distinct disadvantage of the prior art of FIG. 4 on a vintage automobile is the need to completely change and re-wire the purpose of each original wire thus destroying the originality of the vintage automobile. Another disadvantage is the use of multiple CAM sensors 10 and multiple CAM sensor activators 9 unless there is a means of compensating differences in sensor to sensor activation times which translates directly to variation in ignition timing which is contrary to the entire purpose of the apparatus.
Operation of the prior art electronic ignition system of FIG. 4 is facilitated with the aid of FIG. 5. Commutator 5 no longer actuates ignition coils 13 directly by providing a path to engine ground, rather, it now functions solely to signal the position of the engine CAM shaft via two of the former coil primary wires 1. The function of another former coil primary wire 1 is changed to supply a source of dedicated external DC power to the CAM shaft sensors resident on circuit board 21 located within commutator 5. The function of remaining former coil primary wire 1 is changed to provide a connection to engine ground. Referring to FIG. 5, operation is as follows: Ignition switch 18 is closed to provide a source of uninterrupted power from battery 11 via battery wire 12 to electronic control module 15 physically located within coil box 6 and to power electronic sensors located on circuit board 21 physically located within commutator 5 that were previously described with the aid of FIG. 4. Commutator 5 now solely functions to monitor the position of the engine CAM shaft and sends trigger signals via select commutator wires 1 to electronic control module 15 physically located in coil box 6. Electronic control module 15 processes the trigger signals from commutator 5 and turns on semiconductor switches 16 which in turn actuate the firing of coils 13 in synchronization with engine operation. One will note another significant difference in the configuration of FIG. 5 compared to the original prior art of FIG. 2 in that the prior art of FIG. 5 only employs two ignition coils 13 rather than the original four. Engine operation is still possible by exploiting the four stroke cycle of the internal combustion engine; intake, compression, power and exhaust of the four cylinder engine and firing two cylinders in tandem rather than one. The power stroke is fired as usual, however, the other cylinder in the pair is at the end of the exhaust stroke at the time the pair fire which simply does not contribute to the production of engine power. For this reason, this method of engine ignition is well known as the “wasted spark” method to those skilled in the art.
The prior art of FIG. 5 has another disadvantage which are avoided by the present invention. A notable disadvantage of the prior art is the need to eliminate two of the ignition coils and use of the “wasted spark” method. The wasted spark method is functional but is not benign to engine operation especially during engine starting. The wasted spark firing in the cylinder on its exhaust stroke may in fact fire when at the beginning of the next intake cycle depending upon engine timing. Air and fuel may have already begun to enter cylinder if engine timing is retarded causing a puff back or back fire into the carburetor making it difficult to start. This is of particular disadvantage on a early automobile which relies upon hand cranking to start which can become exhausting. The starting procedure of early hand cranked automobiles requires retarding ignition timing to avoid personal injury from engine kick back which helps guarantee air/fuel mixture has already begun to enter the non-firing cylinder when the “wasted” spark occurs in that cylinder. Another disadvantage of the prior art of FIG. 5 is the need to significantly alter the components of the original system. Coil box 6 of FIG. 5 must be either completely rewired or a pre re-wired module must be installed in place of the original coils 13 to implement the wiring and component swaps. This is undesirable on vintage automobiles which are prized for their original appearance and function. Coil box 6 is often easily accessible and inspected to reveal significant modifications have been made to the automobile and it is non-original. Furthermore, substitution of original coils 13 may be necessary to fit all components into coil box 6 result in coil operation that does not mimic original coil operation in which a characteristic “buzz” of the coil primary associated points is heard further diminishing originality.